lostcarnival allows characters with small or non existent bits of canon (IE fan characters from game settings like Shadowrun or what have you), and also has an overarching plot that isn't the whole focus - a lot of what characters can do is based on what they decide to make of their situation. It's a world-travelling fae circus that people get indebted to (either by choice or otherwise) and have to take on year long work contracts to make up for. There are transformation aspects (growing tails, horns, etc) but what you take on is very flexible and the minimum is a pretty small amount.

Characters don't have to become human and there is no restrictions on them staying whatever they are in canon. There is a power cap but it's mostly just to keep people from having a massive edge on other players and from breaking the setting. See what you think!